Electrical steering systems may have an input shaft, that is mechanically linked to a steering handwheel, which is used to transmit a torque required for steering wheels to be steered. An output member is mechanically connected to the wheels to be steered. An electric motor, by which an auxiliary force may be exerted directly or indirectly on the output member, is positioned on the auxiliary force steering system. The input shaft and the output member are connected to each other via a torsionally flexible member so that between the input shaft and the output member a limited twisting motion is possible. In steering systems having a rack-and-pinion gear, the output member is designed as a driving pinion, and is mechanically connected via a gear rack to the steerable wheels of a motor vehicle. The gear rack is mechanically connected to a servo motor developed as an electric motor, via a reducing gear that may be designed as a worm gear. The output member is connected to an electric motor via the worm gear. The main components of the electric motor are a rotor and a stator. The stator is fixed to the housing, and the rotor is connected to a worm shaft of the worm gear via a drive shaft.
Such an electrical steering system is described, for example, in German Published Patent Application No. 197 52 075. This electrical steering system is made up of an electrical motor-driven worm gear system in which the shaft of the worm is held elastically in the gear case. Play is provided between the worm wheel and the worm of the worm gear. The worm is supported shiftably in the axial direction, and is supported on the gear case via elastic elements. Because of this, the negative influences transmitted by the electric motor's actuating drive to the steering system may be reduced.
The electrical steering system described in German Published Patent Application No. 197 52 075 has the disadvantage that noise reduction may be achieved, but not noise suppression. Furthermore, noises appearing at the limit stop during travel are not eliminated. Constant functioning cannot be guaranteed over the entire service life, since the elastic elements will have their characteristics changed by outer influences such as temperature and dirt.
It is an object of the present invention to provide an electrical steering system which may ensure a constant functioning over its entire service life in view of the decoupling of structure-borne noise and damping of the limit stop.